Sonars; sonar apparatus; underwater sonar navigational apparatus; underwater acoustic monitoring apparatus; piezoelectric transducers; piezoelectric transducer apparatus; ultrasonic transducers for underwater communications, imaging, bathymetry, subsurface profiling, and underwater object detection, location, classification and tracking; optical frequency metrology devices; electronic imaging apparatus in the field of bathymetry, subsurface profiling, and underwater object detection, location...